The PI proposes to investigate a new hypothesis that adenoviruses may act as biological mutagens to mutate p53 and BRCA1 human tumor suppressor genes. Mutations in p53 gene (17p13.1) are the most common genetic alteration in human cancer. BRCA1 locus (17q21-22) is linked to early onset familial breast and ovarian cancer and a high metastatic phenotype. Although human adenoviruses produce tumors in rodents and primate models the role of adenoviruses in human cancer remains unresolved. That adenoviruses could act as mutation carcinogens is based on their well established capacity to produce genetic and chromosomal lesions. Oncogenic adenoviruses also produce non random chromosome damage at specific sites including 17q21-22. Our experimental approach takes advantage of several biological systems. The first is the fact that human cells can be investigated for genetic changes by infection with primate adenovirus SA7. The most oncogenic of all adenoviruses, SA7 is highly related to human adenoviruses but is unique among all human and primate serotypes by its semipermissive but non lytic effects in human cells. Secondly a ndw human cell model used by this laboratory (denoted as Hp53ER) takes advantage of a p53 promoter deficient functionally null tumor cell transfected with a p53 gene linked in frame to the gene element for estrogen receptor binding domain. Addition of estrogen to media following adenoviral infection and subsequent stress by hydrogen peroxide treatment permits positive selection of p53 mutated Hp53ER cells that can be investigated for p53 gene and protein changes. Large numbers of non mutated Hp53ER normal cells are apparently destroyed by induction of apoptosis whereas a small fraction of putative adenoviral mutated p53 cells escape and are spared. This system provides a powerful positive selection system for detection of adenoviral mutated cells at p53 locus and provides the capacity to investigate adenoviral genetic interactions after a minimal number of target cell divisions. We have observed several categories of genetic change following adenoviral infection of Hp53ER cells demonstrated a portion of Sa7 E1A gene with a sequence of nucleotides unique to oncogenic adenoviruses. Other clones show loss of p53 exons or other gene construct elements (Daniel et al 1996, Galloway-Barnes et al 1966). Adenoviruses are widespread and persistent in human populations. Investigation of viral mutation effects at tumor suppressor loci may help define mechanisms for understanding how viruses in general and adenoviruses in particular may cause cancer in humans. We propose to investigate: (1) The mechanism by which SA7 infection produces loss of p53 exons. (2) The cellular integration location and random or non- randomness of SA7 genetic material (3) If p53 exon structural deletions correlate with loss of p53 function. (4) What portion of the SA7 genome produces p53 changes. (5) If adenoviral induced changes can be extended to early passage normal diploid human cells. (6) If SA7 produces genetic changes at BRCA1 locus.